Common Variability in the Stable Atmospheric Boundary Layer on Small Space and Time Scales

夜间经常出现的现象是稳定边界层的形成，这是地球表面附近的一层浅的、近乎平静的空气。然而，尽管空气看起来很平静，但仍有持续的运动对近地温度和污染物的扩散有重要影响。该研究奖为分析稳定边界层运动的现有观测数据提供了支持，对如何跟踪这些数据以及如何利用这些信息改进数值天气模式有了新的认识。在与当地现场管理人员协商后，该奖项将解决一个特定的用例，即太平洋西北地区的葡萄园，那里的霜冻会产生重大影响。该奖项下的研究将扩大对小规模、非平稳运动、它们与表面非均质性的相互作用以及它们的随机行为的理解。亚中尺度运动的重点是亚中尺度运动，它的正式定义包括比最大的湍流漩涡更大的尺度上的运动，以及通常被认为是最小的中尺度运动（2公里）。不同类型的小规模运动的一系列案例研究将使用来自9个先前的实地活动的数据和由研究人员开发的一揽子不同的分析方法来构建。该建议的主要目标是：1)量化温度、风矢量和湍流通量的亚中观时空变化，并将这些变化与强迫变量联系起来；2)跟踪数据网络的传播模式，并检查它们与平缓地形引起的地表现象的相互作用以及这种相互作用对湍流通量的影响；3)建立低风速条件下温度和风向短期（非湍流）变化的概率分布，并将其特征与强迫变量联系起来；4)重新分析低风速条件下基于时间平均和空间平均的体积公式中通量和相应的传输系数的变化规律，改进低风速条件下传输系数的公式。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

A regular nighttime occurrence is the development of a stable boundary layer, which is a shallow, near-calm layer of air near the Earth’s surface. However, despite the air seemingly being calm, there are ongoing motions which have important impacts on near-ground temperatures and the dispersion of pollutants. This research award provides support for the analysis of existing observational data on stable boundary layer motions, with a fresh look at how they can be tracked and how that information can be used to improve numerical weather models. A specific use case that this award will address, in consultation with local field managers, is vineyards in the Pacific Northwest where frosts and freezes have a significant impact.The research under this award will expand understanding of small-scale, non-stationary motions, their interaction with surface heterogeneity, and their stochastic behavior. The focus is on submeso motions, which are formally defined to include motions on scales just larger than the largest turbulent eddies and up to scales normally considered to be the smallest mesoscale motions (2km). A sequence of case studies of different types of small-scale motions will be constructed using data from 9 prior field campaigns and a package of different analysis methods that has been developed by the researcher. The main objectives of the proposal are to: 1) Quantify the submeso time and space variability of the temperature, the wind vector, and turbulent fluxes and relate these variations to the forcing variables, 2) Track propagating modes across networks of data and examine their interaction with surface-based phenomena due to gentle topography and the impact of this interaction on turbulent fluxes, 3) Formulate probability distributions for short-term (non-turbulent) variations of the temperature and wind direction for low wind speeds and relate the characteristics of the distributions to the forcing variables, and 4) Reanalyze the behavior of the fluxes and corresponding transfer coefficients in the bulk formula for low wind speeds based on time averaging and based on spatial averaging across the networks and improve formulation of the transfer coefficients for low wind speeds.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.